1. Field of the Invention
The invention relates generally to metal oxide semiconductor field effect transistor (MOSFET) structures, and methods for fabrication thereof. More particularly, the invention relates to metal oxide semiconductor field effect transistor structures that include well defined halo regions, and methods for fabrication thereof.
2. Description of the Related Art
Semiconductor structures include semiconductor substrates within and upon which are formed semiconductor devices, such as but not limited to resistors, transistors, diodes and capacitors. The semiconductor devices are connected and interconnected using patterned conductor layers that are separated by dielectric layers. A particularly common semiconductor device that is used for fabricating semiconductor structures is a metal oxide semiconductor field effect transistor. Such a metal oxide semiconductor field effect transistor comprises a gate located and formed over a gate dielectric that in turn is located and formed over a channel region within a semiconductor substrate that separates a plurality of source and drain regions within the semiconductor substrate. Metal oxide semiconductor field effect transistors have been successfully scaled in dimension over the period of several decades to provide semiconductor circuits with continuously enhanced functionality and continuously enhanced performance.
A particular structural element that is desirable within a metal oxide semiconductor field effect transistor is a halo region of different, and typically opposite, polarity of the source region and the drain region (which hereinafter will be referred to as source and drain regions). Such a halo region, that is located interposed between the source and drain regions and the channel region, is intended to provide enhanced channel isolation within a metal oxide semiconductor field effect transistor. Unfortunately, since halo regions are typically formed using a large angle tilt ion implantation method when a gate and gate dielectric are in place and used as an ion implantation mask, halo region implantation ions routinely compromise performance of field effect transistor devices insofar as halo region implantation ions provide undesirable residual halo region implantation atoms physically at or near a gate dielectric.
Thus, desirable within the semiconductor fabrication art are metal oxide semiconductor field effect transistor structures that include well defined halo regions that are physically separated from gate dielectrics.